2-in-1: catalyst and reaction medium

Abstract

Vials, balls, foils, and pellets used in high-speed ball mills can be catalysts by themselves.

Sustainability Assessment of Mechanochemistry by Using the Twelve Principles of Green Chemistry

“…[168] Although driving chemical reaction by using reactive milling media has been known since antiquity, [169] in recent years a growing interest in the application of this concept in the field of catalysis has reemerged. [170] To date, mechanochemical reactions catalyzed by the milling media are various including Sonogashira crosscouplings, [171] cross-dehydrogenative coupling reactions, [172] and hydrogenations. [173] In an ideal scenario, catalysis would occur on the surface of the milling media to enable a straightforward recovery of the catalyst (e. g., milling container and/or milling bodies) without considerable contamination of the reaction mixture.…”

Direct Mechanocatalysis: Using Milling Balls as Catalysts

“…[6, 21b, 26] The reactions in vibratory ball mills, however,u sually only use one or two balls. [13] Another interesting point is the combination/mixing of vessela nd ball materials. It is often unwise to produce the full vesselo ut of agiven catalytic material, be it due to cost or mechanicalp roperties of the metal in question.…”

“…Screening typical milling materials, this usually leads to ceramics and metals being applied. It is therefore not astonishing that particularly transition metals such as Ag, Cr, Cu, Ni and Pd have been in the focus of direct mechanocatalysis, demonstrating yields rivalling those from homogeneous reactions in solution . The aforementioned metals feature a common property of being quite soft and thus, not very resistant towards abrasion.…”

“…If this proves to be the case, a mechanocatalytic setup should be designed in a way that generates the most oblique collisions during the milling process . Possible approaches to this challenge are the use of smaller grinding equipment or the use of foils made out of the catalytic active metal to increase the probability of an oblique collision …”

“…This demonstrated that milling balls indeed participate in the reaction. They also conducted other reactions and consequently wrote a first mini‐review on this topic . Considering the concept of involving the milling equipment into a reaction, one may even go back as far as the first‐reported mechanochemical reaction at all.…”